Find a general expression for the downwash velocity along the span, and determine the corresponding incidence at the wingtips in the following: 5.7 A wing of symmetrical cross-section has an elliptical planform and is twisted so that, when the attack at the center of the span is 2, the circulation F at a distance y from the wing root is given by r= ro Find a general expression for the downwash velocity along the span, and deter- mine the corresponding incidence at the wingtips. The aspect ratio is 7, and the lift-curve slope for the airfoil section in two-dimensional flow is 5.8. (Answer: arip = 0.566 deg)